US6547784B1 - System and method for placement of a surgical instrument in a body cavity - Google Patents

Abstract

A cryoprobe sheath has at least one positioning element that deploys and retracts to permit the insertion of the cryoprobe into a uterus without using ultrasound or fluoroscopy. Deployment of the positioning element(s) positions the cryoprobe within the uterus permitting even cooling to facilitate cryoablation. The positioning element(s) and sheath may be withdrawn either after tacking the cryoprobe in position by a momentary activation or after a complete activation cycle, with each positioning element pulling through frozen medium in its own track. A guide and filler tube may be employed to infuse the correct quantity of thermally conductive medium into the uterus for cryoablation. The guide and filler tube allows fluid volume and pressure to be measured to avoid inadvertently breaching the uterine wall.

Description

FIELD OF THE INVENTION

The present invention relates generally to systems and methods for optimally positioning surgical instruments within a body cavity, for example, for performing cryosurgery. More particularly, the present invention relates to a system and apparatus for filling a body cavity, such as the uterus with a fluid, e.g., thermally conductive fluid and for facilitating surgical instrument placement at an optimal position within the body cavity, e.g., the uterus, to promote an effective and efficient surgical procedure, such as cryoablation, and for permitting removal of the surgical instrument after use.

BACKGROUND OF THE INVENTION

Cryosurgery has been used for several years for the treatment and ablation of tissue for a variety of therapeutic purposes. For example, cryosurgical probes have been used for ablation of the endometrial lining of the uterus for the treatment of metrorrhagia and other disorders by freezing and killing a layer of endometrial cells. Global ablation of the endometrium is indicated to treat certain conditions wherein the entire intrauterine surface is treated in one therapy cycle. Cryoprobe placement is particularly critical in global ablation procedures in that the cryogenic effect proceeds omnidirectionally outward away from the cryoprobe tip. Accordingly, it is beneficial to optimally position the cryoprobe within the intrauterine cavity to achieve efficient global ablation. Three basic steps are required in cryoendometrial ablation, viz., (i) the introduction of a thermally conductive medium into the uterus to substantially fill the cavity for efficiently conducting heat from the endometrial lining to the cryoprobe;(ii) to place the cryoprobe within the uterus in the most effective position and activate it; and (iii) to remove the cryoprobe.

A method for necrosing endometrial cells of the uterus is disclosed in U.S. Pat. No. 3,924,628 which utilizes an expandable bladder which is inserted in a deflated condition into the uterus on the tip of a probe. After insertion into the uterus, the bladder is inflated with a gas such as nitrogen or freon which also acts as a refrigerant. As it is inflated, the bladder conforms to the interior shape of the uterine cavity. In order to conform the bladder to the shape of the uterine cavity, significant pressures are required which may be uncomfortable for the patient. The bladder also constitutes a thermal barrier to the cryogenic effect, insulating the endometrium from the nitrogen gas. Because of variations in the internal volumetric capacity of uteri within a population, it is not immediately apparent how much thermally conductive fluid is required to fill a given uterus. If fluid pressure alone is used as the indicator of a completely filled intrauterine cavity, the high pressures of distending the bladder and conforming it to the intrauterine shape reduce the relative significance of incremental pressure differences attributable to over-distending/overfilling the cavity. The bladder method therefore leads to a tendency to overfill, resulting in discomfort. As an alternative to a bladder constrained medium, the prior art has also employed unconstrained thermally conductive medium such as saline solution delivered by a catheter into the uterus.

After the thermally conductive medium has been infused into the uterus, a cryoprobe may then be placed therein. The present methods used for cryoendometrial ablation utilize ultrasound to verify the position of the cryoprobe relative to the uterus. Utilization of ultrasound adds complexity, costs and scheduling constraints to the procedure. Further, ultrasound does not guarantee that the cryoprobe will be effectively positioned in the uterus to efficiently freeze the thermally conductive medium. Actuating an improperly positioned cryoprobe fails to achieve optimal necrosing results. Accordingly, it would be beneficial to solve the problems of the prior art as set forth above.

DESCRIPTION OF THE RELATED ART

U.S. Pat. No. 5,275,595 describes a cryosurgical probe which is cooled by a refrigeration system. Cryosurgical treatment of the uterine endometrium and other tissues is described in U.S. Pat. Nos. 3,924,628, 5,647,868 and 5,520,682 and other patents. Use of particulate microcrystalline material, for example diamond suspended in a fluid carbonyl or paraffin, as a heat transfer material is described in U.S. Pat. No. 4,764,845.

U.S. Pat. Nos. 4,016,867, 4,685,474 and 4,204,548 disclose apparatus for measuring the internal dimensions of a uterus and include a caliper-type apparatus which expands to conform to the dimensions of the uterine cavity.

SUMMARY OF THE INVENTION

The limitations of the prior art methods and apparatus for performing surgery in a body cavity using a surgical instrument with a proximal portion and a probe portion are solved by the present invention which includes a positioning assembly for positioning a distal end of the probe portion within the body cavity at a selected position relative thereto. The positioning assembly has at least one positioning element which can assume a retracted position to allow insertion of the positioning assembly into the body cavity and a deployed position in which the positioning element is displaced radially outward relative to the retracted position and relative to an axis of the probe portion when the probe portion is inserted in the body cavity. The positioning element is capable of contacting an interior surface of the body cavity to move the probe portion away from the interior surface when the positioning element is deployed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present invention, reference is made to the following detailed description of various exemplary embodiments considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a cryoprobe apparatus in accordance with a first embodiment of the present invention;

FIG. 2 is a diagrammatic cross-sectional view of a uterus with the tip of the cryoprobe shown in FIG. 1 in place within the uterus;

FIG. 3 is an enlarged view of the tip of the cryoprobe of FIG. 1 showing the retracted position of a positioning apparatus in solid lines and the deployed position in dotted lines;

FIGS. 4 and 5 are diagrammatic views of the withdrawal of positioning elements from a uterus having a thermally conductive material therein;

FIG. 6 is a cross-sectional view of the cryoprobe tip of FIG. 3 taken along section line VI—VI and looking in the direction of the arrows;

FIG. 7 is a cross-sectional view of the cryoprobe shown in FIG. 6 taken along section line VII—VII and looking in the direction of the arrows;

FIG. 8 is a cross-sectional view of the cryoprobe tip shown in FIG. 3 taken along section lines VIII—VIII and looking in the direction of the arrows;

FIG. 9 is a cross-sectional view like FIG. 8 of an alternative embodiment of the present invention;

FIGS. 10-13 are diagrammatic views of four alternative embodiments of positioning assemblies in accordance with the present invention;

FIG. 14 is an enlarged view of a cryoprobe positioning assembly in accordance with an alternative embodiment of the present invention;

FIG. 15 is an enlarged view of a cryoprobe tip sheath and positioning elements in accordance with an alternative embodiment of the present invention;

FIG. 16 is a cross-sectional view of the cryoprobe tip sheath of FIG. 15 taken along cross-section lines XVI—XVI and looking in the direction of the arrows;

FIGS. 17a-dand18a-dare diagrammatic sequential views of the deployment of a positioning element of two alternative embodiments of the present invention;

FIG. 19 is a perspective view of an alternative embodiment of a cryoprobe employing a positioning apparatus in accordance with the present invention;

FIG. 20 is a fragmented perspective view of a cryoprobe tip sheath in accordance with an alternative embodiment of the present invention in the retracted position;

FIG. 21 is a fragmented perspective view of the cryoprobe tip sheath of FIG. 20 in the deployed position;

FIG. 22 is a cross-sectional view of the cryoprobe tip sheath of FIG. 21 taken along section lines XXII—XXII and looking in the direction of the arrows;

FIG. 23 is a fragmented perspective view of a cryoprobe tip sheath in accordance with an alternative embodiment of the present invention;

FIG. 24 is an enlarged view of the cryoprobe tip sheath of FIG. 23;

FIG. 25 is a fragmented perspective view of a cryoprobe tip sheath in accordance with an alternative embodiment of the present invention in the retracted state;

FIG. 26 is a fragmented perspective view of the cryoprobe tip sheath of FIG. 25 in the deployed state;

FIG. 27 is a fragmented perspective view of a cryoprobe tip sheath in accordance with an alternative embodiment of the present invention showing the retracted state in solid lines and the deployed state in dashed lines; and

FIG. 28 is a partially exploded fragmented view of a cryoprobe guide and filler assembly for introducing a thermally conductive medium into a uterus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows acryoprobe assembly10 constructed in accordance with the principles of the present invention and having ahandgrip portion12 which is gripped by the hand of the surgeon. Thehandgrip portion12 has a control panel with a plurality of control buttons14 (freeze, thaw, standby, mode) for controlling, for example, the temperature of the cryoprobe tip86 (see FIG.8). Avisual display16, such as an LCD display, is utilized to display the status of the centering assembly (to be described), the mode, time countdown and/or temperature of thecryoprobe tip86.Cabling18 is provided for connecting thecryoprobe assembly10 to a suitable compressor or other supply of refrigerant gas via aconnector20.

Asheath assembly22 is connected to thehand grip portion12 byadaptor24 which would be threaded or slotted to be removably received onto a mating extension of thehand grip portion12. Thesheath assembly22 is received over the cryoprobe tip86 (FIG. 8) for the purpose of shielding thecryoprobe tip86 from potential contamination by bacteria or viruses that may be present in the uterus of the patient in which it is used. After use, the sheath assembly may be disconnected from the remainder of thecryoprobe10 for separate sterilization, e.g., in an autoclave, sterilizing solution and/or irradiation. Alternatively, thesheath assembly22 may be disposed of after a single use thereby avoiding the expensive and possibly ineffective process of sterilization. Depending upon the cost of thehand grip portion12, it may be preferable to dispose of it after each use if disposal is more cost effective than sterilization. Thesheath assembly22 includes anintermediate shaft26 into which telescopes anactuator tube28. Theintermediate shaft26 may be of greater diameter because it is not introduced into the uterus. Theintermediate shaft26 may house actuating or urging mechanisms for moving theactuator tube28, as will be described below. Theactuator tube28 is coaxially received over aprobe sheath30, the distal portion of which is visible in FIG.1. Theprobe sheath30 is preferably formed from heat conductive material such as stainless steel, is the stationary central portion of theassembly22, and covers thecryoprobe tip86, diminishing the need for extensive sterilization of thecryoprobe10. A pair ofpositioning elements34,35 extend from the distal end ofactuator tube28 and are shown in a deployed position. The deployment of thepositioning elements34,35 may be controlled by an actuator trigger/lever36 guarded byshield38.

The use and structure of aprobe sheath30 is disclosed and described in application Ser. No. 09/087,113 filed May 28, 1998 entitled “Cryosurgical System and Method” owned by the assignee herein and which is incorporated herein by reference for its teachings concerning the construction and operation of cryoprobes and cryoprobe sheaths, e.g., to avoid cross-contamination. The present invention contemplates a variety of options with respect to disposability of elements ranging from sterilization and reuse of the entirety of the instrument to disposal of the entirety after a single use. Because surgical use gives rise to a probability that the patient's bodily fluids will be transferred to theintermediate shaft26 andadapter24, they may be disposable. Depending upon technique, the surgeon's hands may contact the patient's bodily fluids and then subsequently contact the remainder of thecryoprobe assembly10, e.g., when gripping thehandgrip portion12 or pressing thecontrol buttons14, such that theentire probe10 must either be sterilized or disposed of.

FIG. 2 shows the distal end of thesheath assembly22 placed within auterus40 with theactuator tube28 pushed forward to deploy thepositioning elements34 and35. As can be appreciated, thesheath assembly22 extends through the cervix42 at thecervical os50, through the isthmus of theuterine cavity46 with the tip of thesheath30 proximate to thefundus44. Upon deployment, thepositioning elements34 and35 of the embodiment shown in FIG. 2 displace the distal end of theprobe sheath30 laterally within the uterine cavity such that it is approximately centered with respect to thefallopian tubes48. Alternatively, thepositioning elements34,35 can be configured to position the probe sheath to one side or the other of the uterus. Substantiallysymmetrical positioning elements34,35 are especially appropriate for a single probe placement and freeze/thaw cycle.Asymmetric positioning elements34,35 may be utilized in multiple stage procedures wherein the cryoprobe is positioned at a first position within the uterus and a first freeze/thaw cycle initiated followed by repositioning the cryoprobe to a second position within the uterus followed by the initiation of a second freeze/thaw cycle. Multiple freeze/thaw cycles may be initiated as required for the specific procedure undertaken.

Thepositioning elements34,35 deploy within a common or parallel plane that is perpendicular with respect to the orientation of thecontrol buttons14 anddisplay16 such that the surgeon may orient thepositioning elements34,35 relative to the uterus based upon the orientation of thehand grip portion12 relative to the general orientation of the patient's body. In addition to their lateral positioning function, thepositioning elements34 and35 displace the distal tip of thesheath30 away from the wall of the fundus, thus cushioning the tip of thesheath30 and preventing the tip from penetrating thefundus44. Thepositioning elements34,35 may be formed from stainless steel, nitinol tubing, thermoplastics, or wire and may be coated with materials such as a polymer/plastic coating to decrease frictional interaction with a thermally conductive medium.

FIG. 3 shows an enlarged view of the distal end of thesheath assembly22 in its retracted (solid lines) and deployed states (dotted lines). In the retracted position, thepositioning elements34 and35 are received withinchannels54 such that when in the retracted position, the exterior surface is smooth and inserts smoothly through the cervical os. As can be seen in FIG. 3, thepositioning elements34 and35 are contiguous with theactuator shaft tube28 which telescopes over theprobe sheath30. In order for thepositioning elements34 and35 to have their outer surface at the same level as the outer surface of theprobe sheath30 and be received within thechannels54, there is a traversal from the diameter of theactuator tube28 to the level of thechannel54 attransition line55 where an inward bending occurs. In the embodiment shown in FIG. 3, thepositioning elements34 and35 both have afree end58 which extends beyond apivot56 and wraps around the tip of theprobe sheath30 in the retracted position. In this embodiment, onefree end58 overlaps another such that when the positioning elements are deployed, onefree end58 will override theunderlying positioning element34. The other free end, which is not visible in this view, will retain its position overlapping the tip of theprobe sheath30. Thepositioning elements34,35 are free at the ends in order to allow them to be withdrawn from solidified thermally conductive media as can be seen in FIG.4.Thermocouples62 and64 may be provided in thepositioning elements34 and35 in order to obtain a temperature reading at that point. Temperature readings taken on complementary sides of the uterus can indicate whether an even cooling is taking place. In the eventuality that nitinol tubing is used for forming theshims34,35, thermocouples can be threaded through the lumen of the tubing to check the temperature at selected points along the length of eachshim34,35.

FIGS. 4 and 5 diagrammatically depict auterus40 which has been filled with a thermally conductive medium66 such as a sterile jelly, water or saline solution.Viscous media66 such as medical grade jellies, e.g., KY Jelly, silicone jellies, and low freezing point hydrogels are preferred for cryoablation. Acryoprobe sheath assembly122 has been inserted and thepositioning assembly132 actuated. In FIG. 4, thepositioning assembly132 is in the form of a continuous shim orwire134 which is removably attached to thesheath assembly122 at onefree end158 and has a withdrawnend170 which is gripped by a withdrawing mechanism or the hand of the surgeon, allowing theshim134 to be pulled through itstrack168 in the thermally conductive media after it has been frozen. Theshim134 passes through alumen174 provided in thesheath assembly122 and out anexit port178. When thepositioning assembly132 has been withdrawn, thesheath assembly122 may then be withdrawn from theuterus40.

The process for using the present invention therefore includes: (1) filling the uterus with a heatconductive medium66; (2) inserting the sheath assembly122 (and underlying cryoprobe86); and (3) deploying thepositioning apparatus132 to position the tip of the distal end of thesheath assembly122 in a suitable position within the uterus. For global ablation, thesheath assembly122 is preferably centered between thefallopian tubes48 to allow for even cooling ofmedium66 and an even cryogenic effect upon the endometrial lining of theuterus40. After thesheath assembly122 has been positioned by positioningassembly132, thecryogenic probe10 is actuated, freezing the thermally conductive medium66 thereby freezing the endometrial lining. While the medium66 is chilled and/or frozen, thepositioning element134 can be withdrawn through itsown track168 in thefrozen media66 and then through alumen174 provided in thesheath assembly122, and out anoutlet port178. Thesheath assembly122 may then be withdrawn from thefrozen medium66 to allow the removal of thecryoprobe10 from the uterus.

A similar procedure is diagrammatically illustrated in FIG. 5 wherein thepositioning assembly232 includes a pair ofpositioning elements234 and235 each of which has afree end258 such that their simultaneous withdrawal by exerting a force at their withdrawingends270 and272 causes thepositioning elements234,235 to pull through theircorresponding track268 after the heatconductive medium66 is chilled and/or frozen. It should be appreciated that the embodiments of the present invention shown in FIGS. 4 and 5 differ from that which is shown in FIG. 3 in that alumen174,274,276 is provided in thesheath assembly122,222 for slidably receiving acorresponding positioning element134,234,235 to permit the positioning element to be deployed and withdrawn. In FIG. 3, a lumen is not provided, but achannel54 receives thepositioning elements34,35 and deploying and retraction is accomplished by theactuator tube28.

It can be appreciated from the foregoing that the present invention provides a method and apparatus for positioning a cryoprobe in the uterus with mechanical means and without the use of an ultrasound, fluoroscope or any other external equipment. The present invention also permits the positioning device to be removed after the cryoprobe has been positioned. This can be done either before the freezing cycle starts or after freezing has been completed. While FIGS. 4 and 5 have been described as illustrating the removal of thepositioning elements134,234,235 from the medium66 after it has been solidified by the cryogenic probe, the positioning elements can be withdrawn from the medium66 prior to completely solidifying it or it can be withdrawn after a thaw cycle. Thepositioning assembly132 can be used to position the probe in the correct position and thecryoprobe10 activated momentarily to freeze or tack the distal end of thesheath assembly22 in the desired position. The positioning assembly can then be withdrawn prior to completing the cryogenic cycle to solidify the entire medium66 filling the uterine cavity. Accordingly, the present invention can be utilized by inserting the probe, deploying thepositioning assembly132 and then tacking the probe with a momentary actuation followed by withdrawal of thepositioning assembly132. As shown in FIGS. 4 and 5, the centeringassembly132 can also be removed from the uterus after the freezing cycle has been completed and the heat conductive medium66 solidified. As can be appreciated from the foregoing, the present invention provides lateral centering but also can provide spacing of the distal end of thesheath assembly22 from the fundus, both for the purpose for positioning the probe longitudinally and to provide a cushioning effect to prevent the uterus from being penetrated or injured by thecryogenic probe10.

FIGS. 6 and 7 show further structural details of the embodiment of the present invention depicted in FIG.3. As noted above, thepositioning elements34 and35 extend from theactuator tube28 and attransition point55 extend intochannels54 such that they do not extend above the surface of theprobe sheath30 in the area where it is inserted through the cervical os. Theactuator tube28 is preferably manufactured to close tolerances relative to thesheath30 such that it can readily be slid through the cervical os without significant radial displacement of the cervix. The tip of thetube28 can be tapered inwardly to further facilitate a gentle introduction of thetube28 through the cervical os. As can be appreciated from FIGS. 6 and 7, thesheath30 has acryoprobe lumen82 extending through the center thereof for admitting acryoprobe tip86. The dimensions selected for these figures are used for illustration purposes only, in that the optimum dimensions, e.g., the wall thickness ofsheath30, are minimal to maximize heat transfer and to minimize the diameter of thesheath assembly22 that is introduced into the uterus.

FIG. 8 illustrates how theprobe sheath30 with blinddistal end31 andlumen84 coaxially covers thecryoprobe tip86 with a peripheral space therebetween filled with a heat conductive paste as described in application Ser. No. 09/087,113 which has been incorporated herein by reference. Thecryoprobe tip86 is cooled using known principles and apparatus, for example as referred to in application Ser. No. 09/087,113, and typically incorporates arefrigerant discharge tube88 proximate to the distal end of thecryoprobe tip86 such that when refrigerant in a liquefied or semi-liquid state exits therefrigerant discharge tube88 and converts to a gas, the heat of vaporization is absorbed from thecryoprobe tip86 and its surrounding environment. The expanded refrigerant gas is then conducted back to its origins or is vented to the atmosphere, depending upon the particular cryoprobe technology employed. FIG. 8 illustrates in cross-section how thepositioning elements34 and35 extend from theactuator tube28 and descend from the outer periphery of thesheath30 into thechannel54 at thetransition point55. The overlapping free ends58 of thepositioning elements34 and35 can be seen positioned against apivot56 provided at the distal end of theprobe shield30. Theprobe shield30 may have a channel or groove carved therein to accommodate thefree end58 which contacts it, i.e., thefree end58 associated withpositioning element35. The otherfree end58 ofpositioning element34overlaps positioning element35 and is displaced upward when the positioning elements are deployed by theactuator tube28. Thepositioning elements34,35 may have a variable width, e.g., with the portions proximate free ends58 being narrower than the portion which contacts the uterus, In this respect, it is beneficial for the positioning elements to be wider at their contact surfaces because the broader the area of contact, the less force per unit area is exerted on the uterus by the positioning elements upon deployment. While FIG. 8 illustrates an embodiment wherein thepositioning elements34,35 overlap, they can also be laterally offset as shown in FIG. 15, to be described below.

FIG. 9 depicts an alternative embodiment in which a pair oflumens174 and176 slidingly accommodate acontinuous positioning element134 which passes therethrough down to the base of the cryoprobe sheath where an actuator mechanism deploys and retracts it. In this embodiment, one of the ends of thecontinuous positioning element134 needs to be removably inserted in a receiver. When the other end of thepositioning element134 is pulled to withdraw it from the intrauterine space, the free end can travel through its associated lumen and the heat conductive medium in order to be withdrawn from the deployed position, as shown in FIG.4. Alternatively, thecontinuous positioning element134 may be frangible at a point along its length.

Four different strategies for positioning element deployment and use are shown in FIGS. 10-13. In each of FIGS.10,11,12 and13, thepositioning assembly132,232,332,432 includes anactuator portion96, atransition portion94 and apositioning element portion191,291,391,491. The positioning element portions diverge from thetransition portion94 at adivergence point93. That is, thedivergence point93 is where the positioning elements, e.g.,234,235 diverge from their generally parallel retracted position to their laterally expanded deployed position. With reference to the embodiment shown in FIG. 8, thetransition portion94 is equivalent to theactuator tube28. Thedivergence point93 in the embodiment shown in FIG. 8 is approximately at thetransition line55. In the embodiment shown in FIG. 9, thetransition region94 includes thelumens174 and176 and the divergence points93 occur at the distal openings of thelumens174 and176 as they enter the channels154. In both FIGS. 8 and 9, theactuator mechanism96 is not shown.

As noted above, the positioning mechanism of the present invention may utilize apositioning element pivot56 which urges thepositioning assembly132 into its cardioid shape when deployed. In order to be withdrawn from the uterus after having accomplished the positioning function, the positioning elements, e.g.,34,35, must have a free end or ends such that they may be withdrawn through the thermally conductive medium if it is solidified. In FIG. 10, the free end is provided by afrangible point192aor192bin an otherwisecontinuous positioning element134. The frangible point may also exist at thedivergence point93 or may reside in thetransition portion94. In any case, when theactuator mechanism96 is actuated in the direction of retraction, the forces conducted through thetransition portion94 to thepositioning element portion191 cause thefrangible point192aand192bto break and allow thepositioning element134 to travel in opposite directions, as shown in FIG. 5, to be withdrawn from the uterus. As an alternative to breaking, one end of thepositioning elements134 may be tucked into a suitable slot provided in thetransition portion94.

FIG. 11 illustrates an embodiment of the present invention utilizing a pair ofpositioning elements234,235 that have a preset cardioid shape when in the relaxed state. Each of the prestressed,preshaped positioning elements234,235 is attached to thetransition portion94 and diverge from thesheath30 when thetransition portion94 travels towards the tip of the sheath30 (see FIG.1). In FIG. 11, thepositioning elements234,235 are shown in their retracted state in solid lines and in the deployed state in dotted lines. Each of theprestressed positioning elements234,235 has afree end292 which would be received in a suitable recess provided at the tip of the probe sheath30 (not shown).

FIG. 12 shows an embodiment of the present invention wherein thepositioning elements334,335 have ends392 which overlap the tip of theprobe sheath30. The degree of overlap can be similar to FIG. 3 or greater as shown in the embodiment of FIG. 15 which will be further described below in reference to that figure.

FIG. 13 diagrammatically shows an embodiment of the present invention utilizing a pair ofpositioning elements434,435 which terminate atfree ends492 which do not extend beyond the tip of theprobe sheath30 but rather insert into suitable recesses along the length of thesheath30 proximate the distal end thereof. This embodiment is further described and illustrated in FIGS. 23-27 below. Thepositioning elements434,435 may either be straight in their relaxed state and urged into a cardioid shape or may be prestressed to assume a relaxed shape that facilitates positioning thecryoprobe10.

FIG. 14 illustrates diagrammatically some additional features that may be incorporated into the present invention. In general, it is noted that the positioning assembly32 has certain movable parts that move relative to a stationary element or base member, namely theprobe sheath30. Thepositioning elements34,35 are deployed and retracted via the action of anactuator mechanism96 acting upon atransition portion94 which urges thepositioning elements34,35 into a cardioid shape beginning at the point ofdivergence93. Theactuator96 may be any known mechanical actuation mechanism for sliding one element relative to another. In the embodiment shown, theactuator mechanism96 is a toothed collar which rides over theprobe sheath30 or a basal element in structural continuity with theprobe sheath30. As theactuator96 has teeth, it may be used to interact with another toothed member such as agear wheel97 rotatably attached toextension95 and driven by a ratchet and trigger36 (FIG. 1) that the operator of the device may employ to deploy and retract thepositioning elements34 and35. Alternatively, a hand-wheel or hand-crank can turn thegear wheel97 or a simple thumb slide may be provided to allow the surgeon to moveactuator element96 toward the distal end of theprobe sheath30. While acylindrical actuator collar96 is depicted, theactuator96 could be an elongated toothed member (rack) sliding within a track provided in theprobe sheath30 or other structural support for thesheath30. As noted above, thetransition portion94 of the positioning assembly32 may be in the form of a tubular member which is structurally integrated with theactuator96 at one end and with thepositioning elements34 and35 at the other end. As further noted above, thetransition portion94 may also be integral with the sheath or rigidly affixed to the sheath in the form of a pair of lumens extending therethrough to accommodate thepositioning elements34,35 from thedivergence point93 back to theactuator element96.

In FIG. 14, thepositioning elements34 and35 are of two different types for the purposes of showing the different possibilities for constructing and using the positioning assembly32. Positioningelement34 passes behindpivot56 to endretention point98a. Positioningelement35 shows an alternative form of end placement and retention in that the free end of the positioning element is retained in a receptacle98b positioned further from the tip and without utilizing apivot56. The deployed shape of thepositioning elements34 and35 depend on several factors including the relaxed shape of the positioning element, the torsional rigidity of the positioning element along various points of its length, the presence/location of a pivot and the location of the end retention point98. In addition to the resultant deployed shape of thepositioning elements34 and35, as defined by the various mechanical and dimensional attributes of the positioning elements and their interaction with the sheath assembly, the deployed shape will also be effected by its interaction with the uterus.

FIG. 14 depicts an embodiment wherein thepositioning elements34 and35 are asymmetric. This condition can be utilized to perform a two step ablation procedure wherein theasymmetric positioning elements34,35 position a cryoprobe off-center in the uterus. The cryoprobe is then activated, freezing the thermal conductive medium on the side of the uterus in which the cryoprobe has been positioned. The cryoprobe is then removed from its first position, the positioning elements reoriented in the opposite direction and redeployed to position the cryoprobe on the opposite side of the uterus which then is treated by actuating the cryoprobe. As an alternative to asymmetric positioning elements, thepositioning elements34,35 may be independently deployable such that a two step ablation with repositioning may be accomplished by actuating a first positioning element to displace the cryoprobe in a first direction followed by actuation. A second step follows removal of the cryoprobe from its first position, deployment of the second positioning element and a subsequent actuation of the cryoprobe to freeze the second side. In addition to positioning and freezing, a thaw cycle can be included in the procedure at each sequential positioning.

In general, it is desirable to exert the minimum force for centering, insertion and/or otherwise maneuvering thecryoprobe10 and the positioning assembly32 within the uterus to avoid trauma to the uterus. Accordingly, the positioning element tension should be selected such that it can position theprobe10 without placing undue forces on the uterus. FIG. 14 illustrates three additional features that may be incorporated into the present invention to minimize the risk of subjecting the uterus to unnecessary trauma. Due to the fact that uteri vary in dimensions based upon the individual and their age, genetic makeup, etc., the centering apparatus will need to be deployed to a greater or lesser extent for larger or smaller intrauterine cavities, respectively. As is known in the art, intrauterine dimensions may be measured by intrauterine caliper and sound devices. Upon ascertaining the intrauterine dimensions for a particular patient, the degree of deployment of the positioning device of the present invention can be tailored to the particular patient and her specific intrauterine dimensions by means of an adjustable deployment stop/control mechanism which can operate on thetransition portion94 and/or theactuator mechanism96,97. FIG. 14 illustrates a deploymenttravel limiter slot100 provided in thetransition portion94 and a plurality of stop buttons or pins102 which may be raised or lowered to engage the edge of theslot100 in order to limit the motion of thetransition portion94 and thereby the deployment travel of thetransition portion94. Alternatively, an adjustable travel stop could act againstactuator elements96,97,98.

As yet another safety mechanism, aforce limiting spring108 may be introduced between the actuator96 and thetransition portion94. Theforce limiting spring108 can be used to absorb the deployment travel attributable to theactuator96 in the eventuality thatpositioning elements34,35 encounter intrauterine resistance to deployment. In this manner, thespring108 absorbs the force that would otherwise be exerted on thepositioning elements34,35, for example when centering the probe in a uterus that has smaller internal dimensions than the average.

As yet another feature to avoid placing excessive forces on thepositioning elements34,35 and the uterus, adeployment spring104 may be utilized to supply the urging force propelling theactuator96 forward, resulting in the deployment of thepositioning elements34,35. In an embodiment utilizing thedeployment spring104, the actuator gearing or linkage, for example96,97, would be used as a brake which is released to permit thedeployment spring104 to actuate the deployment of thepositioning elements34,35. The actuatingmechanisms96,97 can then be used to retract the positioning elements against the force of the deployingspring104. By utilizing thedeployment spring104, the force exerted on thepositioning elements34,35 is limited to that which is inherent in the resilience of thespring104.

FIGS. 15 and 16 depict an embodiment of the present invention having offset overlappingpositioning elements335,334. As can be appreciated from FIG. 15, the transition portion constitutes alumen374 through aprobe sheath330 which terminates in a recessedchannel354 that extends up and over the distal end of theprobe sheath330. Thechannel354 continues over to the other side of theprobe sheath330 to accommodate a free end of eachpositioning element392. As a consequence, adiversion point393 is the opening of thelumen374 into thechannel354 and thepivot356 is where thechannel354 reenters thelumen374 proximate the otherfree end392 of the positioning element.

FIGS. 17 and 18 depict positioning element deployment shape in a sequence of progressions of increasing positioning element deployment. For simplicity, only onepositioning element34 is shown. An asymmetric or symmetrically displacedpositioning element35 could be deployed opposite to thepositioning element34 shown. In FIG. 17a-d, thepivot56 is located centrally at the tip of theprobe sheath30. In this respect then, the positioning element shown in FIG. 17 deploys in the manner of the embodiment depicted in FIG.3. When thepivot56 is located centrally on theprobe sheath30 tip, thepositioning element34 tends to displace in an x direction, i.e., towards the fallopian tubes before displacing in the y direction, i.e., in the direction of the fundus. When fully deployed, as shown in FIG. 17d, it can be appreciated that the displacement in the x direction of the deployed shim is greater than its displacement in the y direction.

In FIG. 18, thepivot56 is displaced from the center by angle α. This displacement results in a more even distribution of x and y displacement as the positioning element is deployed. Upon full deployment, the positioning element shown in FIG. 18dhas approximately equal x and y displacements, i.e., displacements in the direction of the fallopian tubes and in the direction of the fundus. It can be concluded therefore that thepivot56 displacement by angle α shown in FIG. 18 results in a greater cushioning effect of the tip and exerts a greater retrograde force that urges the tip away from the fundus. Given the potential for the cryoprobe to partially or completely penetrate the uterus through excessive forward travel under excessive force, the cushioning effect shown in FIG. 18 is desirable to prevent inadvertent penetration of the uterine wall.

FIG. 19 shows an alternative embodiment of the present invention wherein theintermediate shaft526 andactuator tube528 are split along one side permitting theintermediate shaft526 andactuator tube528 to be slipped over theprobe sheath530 laterally. Theactuator tube528 can be pushed forward to deploy thepositioning elements534 in order to position the cryoprobe within the uterus. Once centered, the cryoprobe can be activated to tack the tip in position in the uterus. When slid forward beyond theadaptor524, theintermediate shaft526 andactuator tube528 can then be spread along the slit527 by grasping the hand grips525 and laterally slipped free of thesheath530 to withdraw theintermediate shaft526 andactuator tube528 from the uterus and to withdraw the attachedpositioning elements534 whose free ends are overlapped at the distal end of theprobe sheath530. In the embodiment shown in FIG. 19, theactuator tube528 andintermediate shaft526 simply slide telescopically on thesheath530. An alternative actuating mechanism could be employed operating from ahandgrip portion512 and urging theintermediate shaft526 forward to deploy thepositioning elements534,535 either using a mechanical mechanism or under spring pressure as described above.

FIGS. 20-22 depict an alternative embodiment of the present invention utilizing a pair of positioning coils635,634 which are wound about aninternal probe sheath630. Anexterior actuator tube628 is attached to one end of each of the coils proximate theopenings611 in theactuator tube628. The other end of eachcoil634,635 is attached to theprobe sheath tube630. When in a retracted position, the coils are tightly wound about theprobe sheath630 and do not protrude beyond theopenings611. When the apparatus is placed in the uterus, theexterior actuator tube628 can be rotated relative to theinterior probe sheath630 thereby unraveling the shim coils634,635 causing them to protrude outwardly to accomplish the centering function. After the centering function has been accomplished, thecoils634,635 may be retracted by rotating theprobe sheath630 in the reverse direction to recoil them to the retracted position. Alternatively, theactuator tube628 may continue to be turned in the deploying direction which eventually will cause the wrapping of thecoils634,635 about theprobe sheath630 and cause the free ends of thecoils634,635 which are attached to theactuator tube628 to be pulled from their retaining receptacles. This latter method of operation is also amenable to operation within a frozen thermal conductive medium in that thecoils634,635 can be withdrawn along their own track through the solidified medium. Once thecoils634,635 are withdrawn, the cryoprobe can be withdrawn from the uterus and the thermal transfer medium either in its liquefied or solidified state.

FIGS. 23 and 24 show an alternative embodiment of the present invention whereinpositioning elements734 and735 pass throughlumens774 provided in theprobe sheath730. The lumens terminate at the upper end inchannels754 for receiving thepositioning elements734,735 when in a retracted position such that the positioning elements do not extend above the surface of theprobe sheath730. FIGS. 23 and 24 are fragmented, with portions of theprobe sheath730 removed proximate thepositioning elements734,735 to show their position in the retracted and deployed positions. FIG. 24 is an enlarged view of the distal tip portion of thesheath730 showing positioning element retention holes798 which receive the upper end of thepositioning elements735,734 and permit the positioning elements to be withdrawn from thetip730 after deployment and tacking or freezing of the thermally conductive medium. As can be seen, thereceptacles798 receive a free end of thepositioning elements734,735 and thereby restrain the positioning element free end from pushing forward beyond the tip of thesheath730 when the positioning element is pushed in the deploying direction. When retracted however, the free end of thepositioning elements735,734 can be withdrawn from thereceptacle798.

FIGS. 25 and 26 show another alternative embodiment of the present invention whereinpositioning elements834 extend from anactuator tube828 which is coaxially placed over theprobe sheath830 and is rotatable relative thereto. When in the undeployed position shown in FIG. 25, thepositioning elements834 are retained at their free ends proximate the tip of thesheath830 in suitable retention holes898. To deploy thepositioning elements834 and provide the centering function, theactuator tube828 is rotated, uncoiling the positioning elements from their spirally wound position about theprobe sheath830. After the positioning function has been completed, i.e., either after the tacking of the probe sheath to the fundus or after the freezing process has been initiated to solidify the thermally conductive medium, theactuator tube828 can then be withdrawn in a rearward fashion to pull thepositioning elements834 from their positions in the retention holes898.

FIG. 27 shows an alternative embodiment whereinactuator tube928 has a pair ofpre-tensioned positioning elements934,935 having a relaxed shape which is biased outwards to perform the positioning function. In order to utilize the embodiment shown in FIG. 27, thepositioning elements934,935 are pressed together and their ends are inserted insuitable receptacles998 proximate the tip of theprobe sheath930 where they are retained during the placement of the cryoprobe. Thepositioning elements934,935 are deployed by withdrawing theactuator tube928 rearwardly relative to theprobe sheath930 thereby freeing the ends of thepositioning elements934 and935 from theirreceivers998,998 allowing the positioning elements to expand outwardly and to perform the positioning function.

FIG. 28 shows another aspect of the present invention, namely a probe guide andfiller assembly1000 which is used to introduce the thermally conductive medium into the uterus and to serve as a guide to a cryogenic probe. The guide andfiller assembly1000 depicted in FIG. 28 may employ a positioning assembly as described above, e.g., utilizingpositioning elements1042,1043 that are deployed and retracted, or it may have an open distal end which permits a cryoprobe sheath having a positioning assembly thereon to be inserted through theguide tube1138 for deployment of the centering apparatus.

When placing a catheter for infusing thermally conductive medium in the uterine cavity, it is essential to be able to determine whether the catheter has perforated the uterus. By distending the uterus with fluid under a given pressure using a limited amount of fluid, one can verify that the uterus is intact and has not been perforated. Measuring the pressure and volume of fluid introduced into the uterus can be used to determine that the introducing catheter has neither perforated the uterus nor has created a false passage by partially embedding itself into the uterine wall in that a perforated uterus would permit a larger volume of fluid to be infused at low pressure into the extra-uterine spaces of the body. In the instance of a partially penetrated uterine wall or false passage, a large amount of pressure would be ineffective to infuse even a small volume of thermally conductive fluid due to the fact that the fluid cannot pass into the uterine cavity and is plugged by its terminating in the uterine wall.

The probe guide andfiller assembly1000 operates upon the following principals. The volume of a normal uterus falls in the range between 6 and 30 mm. If one is not able to inject a minimum amount of fluid into the uterus, one can assume that a introducerfluid injection tube1038 has created a “false passage” (it has been inserted to an intermediate depth into the intrauterine wall). By specifying a minimum amount of liquid at a maximum pressure one can test for false passage. On the other hand, if the uterus is perforated, the pressurized fluid can flow out the perforation. By specifying a maximum volume at a minimum pressure, one can use the present invention to test for a perforated uterus. The probe guide andfiller assembly1000 accomplishes this monitoring of volume and pressure and includes amultiport body1010 having afluid inlet port1012 which includes a one-way check valve1014.Inlet port1012 communicates with a lumen extending downtube1038 and terminating inoutlet1040. Apressure sensor port1018 communicates with the fluid conduit extending betweeninlet1012 andoutlet port1040. Thepressure sensor port1018 accommodates apressure sensor assembly1020 including a fluidpressure sensing piston1022 and aplunger1024 which receives aspring1026 about astem1028 thereof. Acap1030 with anopening1032 is removably received within the pressure sensor port with thestem1028 projecting through theopening1032. Fluid pressure acting against thepiston1022 urges theplunger1024 against thespring1026 and causes thestem1028 to project through theopening1032 to varying degrees. Thestem1028 preferably has graduations marked thereon to quantify the pressure which thepressure sensor assembly1020 indicates.

Themultiport body1010 also includes acentral probe lumen1016 for receiving a cryoprobe which may be provided with a check valve to prevent thermally conductive fluid from exiting the uterus throughlumen1016. Ahandle1034 is utilized to assist in grasping the guide andfiller assembly1000 and includes aprobe funnel1036 to assist in introducing a cryoprobe into theprobe lumen1016. Anelongated guide tube1038 is utilized for introducing the guide andfiller assembly1000 into the uterus and hasdischarge outlet1040 at one end through which the fluid medium is discharged. Thetube1038 may also include a positioning device in the form ofpositioning elements1042,1043 at the distal end thereof for positioning the apparatus in the uterus. In use, a syringe is filled with the specified thermally conductive fluid and is attached to theinjection valve1014. The syringe can then be depressed urging the fluid through themultiport body1010 and through an associated lumen provided in the fluid delivery andguide tube1038 which discharges fromoutlet port1040 into the uterus. Thepressure sensor1020 is in communication with the lumen extending from theinjection port1012 toport1040 in order to sense the pressure within that lumen as well as within the uterus. When thepressure sensor1020 indicates a predetermined maximum pressure, a reading of the volume injected by the syringe can be made. If the volume injected falls within an acceptable range, one can infer that the guide andfiller assembly1000 has been safely placed within the uterine cavity and a suitable amount of thermally conductive medium introduced. Under certain circumstances, such as when the cervix has previously been dilated, it may be necessary to create a seal at the internal cervical os to prevent pressurized fluid from escaping around the probe at the cervix. This situation arises if the cervix has been dilated for the purpose of a hysteroscopic examination. A seal can be provided by a conventional balloon, elastic ring or cup disposed around the perimeter of theguide tube1038 at a position where it would align with the cervical os. The use of a seal allows for the use of a less viscous fluid that fills the uterine cavity more easily and allows better pressure detection. The seal may operate internally to the cervix or externally.

After the guide andfiller assembly1000 has been employed to fill the uterus with a suitable quantity of thermally conductive medium, the cryoprobe can then be inserted through thelumen1016 and cryogenic ablation can then be conducted. Alternatively, the cryoprobe can be inserted into the uterus throughlumen1016 prior to the infusion of thermally conductive media. As noted above, the guide andfiller assembly1000 can incorporate a positioning apparatus such aspositioning elements1042,1043 that permit the assembly to be positioned correctly before initiation of the cryogenic procedure.

As yet a further alternative, aguide tube1138 can have an open end to permit the passage of asound1046 and/or a cryoprobe. The open-ended version of theguide tube1138 permits the use of aflexible sound1044 with asoft tip1046 and a calibratedend1048 to be inserted into the uterus. Given that the distance from the opening at the tip of theguide tube1138 to the opening in thecryoprobe funnel1036 is a fixed distance, thesound1044 which is inserted into the uterus can then serve as a guide for placing the guide andfiller assembly1000 into the uterus. Theassembly1000 may be inserted over a fully insertedsound1044 starting at thecalibration end1048. Theassembly1000 is telescoped over thesound1044 until it enters the uterus with the calibratedend1048 protruding from the opening in theprobe funnel1036 where it assumes a predetermined depth of insertion relative thereto with thesoft end1046 protruding to some predetermined extent from the opening in the tip of theguide tube1138. Theflexible sound1044 can then be removed and a cryoprobe inserted in its place in order to perform the cryogenic procedure. Accordingly, the present invention provides a complete system that can deliver the thermally conductive medium, seal the uterus, detect thermal fluid pressure and center the cryogenic probe for cryoendometrial ablation. The system can be operated with the single insertion of anouter sheath1038 that has adischarge port1040 through which the thermal fluid is ejected to fill the uterine cavity. Another port, i.e., thepressure sensor port1018 on theassembly1000 accommodates apressure sensor1020 and yet anotherport1016 receives a cryoprobe. Apositioning assembly1042,1043 may be incorporated on theguide tube1038 or on the cryoprobe. The present invention also provides a method for positioning a cryoprobe in the uterus by mechanical means and without the use of an ultrasound, fluoroscope or any other external equipment.

The positioning mechanism can be removed either before the freezing cycle has begun, after tacking, or after freezing has been completed. The present invention permits the cryoprobe itself and any associated sheath to be removed after freezing and before the thermally conductive medium thaws. The positioning apparatus disclosed herein may be incorporated into the cryoprobe tip itself, a cryoprobe sheath, a guide and filler assembly or any other form of introducer tube or sound.

It should be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications therein without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims (27)

What is claimed is:

1. An apparatus for facilitating surgery within a body cavity using a cryoprobe having a proximal portion and a probe portion extending therefrom for insertion into the body cavity, comprising:

a positioning assembly for positioning a distal end of the probe portion within the body cavity at a selected position relative thereto, said positioning assembly having a positioning element which can assume a retracted position to allow insertion of said positioning assembly within the body cavity and a deployed position in which said positioning element is displaced radially outward relative to said retracted position and relative to an axis of the probe portion when the probe portion is inserted in the body cavity, said positioning element capable of contacting an interior surface of the body cavity to move the probe portion away from the interior surface when said positioning element is deployed;

a tubular probe sheath with a lumen and a blind distal end, said probe sheath adapted to accommodate the probe portion of the cryoprobe therein and supporting a distal end of said positioning element in the retracted and deployed positions;

an actuator for moving a proximal end of said positioning element relative to said probe sheath to deploy and retract said positioning element, said positioning element being in greater overall proximity to said probe sheath when in the retracted position to facilitate inserting said positioning assembly in the body cavity and diverging therefrom to a greater degree when in the deployed position.

2. The apparatus ofclaim 1, further including a plurality of positioning elements each of said distal ends thereof being free to disassociate from said probe sheath when pulled distally and each of said proximal ends thereof connected to said actuator, said actuator moving each of said proximal ends for deploying and retracting said positioning elements.

3. The apparatus ofclaim 2, wherein said positioning elements are positioned and shaped so as to cumulatively assume a substantially symmetric shape in the deployed position.

4. The apparatus ofclaim 2, wherein said positioning elements are positioned and shaped so as to cumulatively assume a substantially asymmetric shape in the deployed position.

5. The apparatus ofclaim 2, wherein said positioning elements are pre-tensioned to assume a deployed state when unconstrained, such that said actuator releases said shims to assume their relaxed shape to deploy said shims.

6. The apparatus ofclaim 2, wherein said positioning elements are laterally offset relative to each other.

7. The apparatus ofclaim 2, wherein said distal ends of said positioning elements overlap one another.

8. The apparatus ofclaim 2, wherein said positioning elements are spirally wound about said base member in the retracted position and are unwound to assume the deployed position.

9. The apparatus ofclaim 2, wherein said distal end of each of said positioning elements are inserted in a corresponding receptacle formed in said base member to allow said distal ends to be withdrawn from their corresponding receptacles when said positioning elements are pulled in a proximal direction relative to said base member.

10. The apparatus ofclaim 2, wherein said plurality of positioning elements are coiled about said base member in the retracted position and are uncoiled to assume the deployed position.

11. The apparatus ofclaim 1, wherein said probe sheath has a channel to receive said positioning element therein such that said positioning element does not protrude above the surface of said probe sheath when in the retracted position.

12. The apparatus ofclaim 11, wherein said channel terminates near said distal end of said probe sheath in a pivot, said positioning element passing beneath said pivot and being restrained by said pivot when deployed to prevent said positioning element from diverging from said probe sheath at said pivot.

13. The apparatus ofclaim 1, wherein said positioning element extends from said actuator to said channel by passing through a lumen in said probe sheath.

14. The apparatus ofclaim 1, further including an actuator tube interposed between said actuator and said positioning element, said proximal end of said positioning element being attached to said actuator tube, said actuator tube telescoping over said base member, said actuator urging a proximal end of said actuator tube in a distal direction to deploy said positioning element.

15. The apparatus ofclaim 1, wherein said positioning element is frangible at a point along its length.

16. The apparatus ofclaim 1, wherein said probe sheath has an open end that permits said cryoprobe surgical instrument to protrude through said open end.

17. The apparatus ofclaim 1, wherein said probe sheath has a longitudinal slit along its length to permit said probe sheath to be laterally removed from a cryoprobe inserted into said lumen.

18. The apparatus ofclaim 1, further including a deployment stop for restricting deployment travel of said positioning element to a selected degree.

19. The apparatus ofclaim 18, wherein said deployment stop has a plurality of settings for varying the extent of deployment.

20. The apparatus ofclaim 1, further including a resilient force limiting member interposed between said actuator and said positioning element, said force limiting member absorbing excess force that would otherwise be transferred to said positioning element when said positioning element encounters the interior surface of the body cavity.

21. The apparatus ofclaim 1, further including a resilient urging member for automatically urging said positioning element to the deployed position, said urging member having a selected potential energy for deploying said positioning element at a maximum selected force against the interior surface of the body cavity.

22. The apparatus ofclaim 1, wherein said positioning and assembly includes a cryoprobe having a pivot affixed at a distal end thereof, said positioning element threading under said pivot.

23. The apparatus ofclaim 1, wherein said positioning element is a wire.

24. The apparatus ofclaim 1, wherein said positioning element is coated with a polymer.

25. The apparatus ofclaim 1, wherein said positioning element is formed from tubular material.

26. The apparatus ofclaim 1, further including at least one thermocouple attached to said positioning element for ascertaining the temperature of said positioning element at a selected point along its length.

27. An apparatus for facilitating surgery within a body cavity using a cryoprobe having a proximal portion and a probe portion extending therefrom for insertion into the body cavity, comprising:

a positioning assembly for positioning a distal end of the probe portion within the body cavity at a selected position relative thereto, said positioning assembly having a positioning element which can assume a retracted position to allow insertion of said positioning assembly within the body cavity and a deployed position in which said positioning element is displaced radially outward relative to said retracted position and relative to an axis of the probe portion when the probe portion is inserted in the body cavity, said positioning element capable of contacting an interior surface of the body cavity and adapted to move the probe portion away from the interior surface when said positioning element is deployed;

a tubular probe sheath with a lumen and a distal end, said distal end of said probe sheath adapted to accommodate and axially restrain the probe portion of the cryoprobe therein; and

an actuator for moving a proximal end of said positioning element relative to said probe sheath to deploy and retract said positioning element, said positioning element being in greater overall proximity to said probe sheath when in said retracted position to facilitate inserting said positioning assembly in the body cavity and diverging to a greater degree when in said deployed position; said positioning element being displaceable axially relative to the probe portion to move said distal end of said probe sheath and the probe portion away from the interior surface in an axial direction.

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